Page 112 - Molecular features of low-grade developmental brain tumours

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pathways from GSEA to were enriched for validated targets of 45/94 of the differentially expressed miRNAs (Fisher’s exact test, adjusted p-value<0.05). Pathways enriched for a specific miRNA are indicted with a green box. e. Validation of selected differentially expressed miRNAs (miRNA-20a-5p, miRNA-34a- 5p, miRNA-130b-3p and miRNA-181a-5p) in SEGA (n=19) compared to control tissue (n=8) using Taqman
PCR. **p-value<0.01, ***p-value<0.001, Mann-Whitney U test.
the mTORC1 and MAPK/ERK pathway was most efficient in decreasing proliferation after 48 hours and cell viability after 3 days of treatment compared to mTORC1 or ERK inhibition alone 28. This suggests that combined therapy may be only beneficial over a longer period of time. However, considering the side effects, it may also be difficult to treat patients with multiple inhibitors at the same time 79,80. Therefore, therapeutic interventions resulting in decreased MAPK signaling in SEGA could be used as an alternative to the current treatments available, especially in TSC patients that do not adequately respond to mTORC1 inhibitors. However, the need for more specific treatment remains. Since the MAPK/ERK pathway is known to regulate cell proliferation but has also been linked to epilepsy, patients with other TSC lesions, such as tubers, may also benefit from treatment with MAPK/ERK inhibitors, however further investigation is highly needed 81-86.
Figure 6. Relative expression of LAMTOR genes after transfection with miRNA-20a-5p mimic in fetal astrocytes. Taqman PCR of miRNA-20a-5p (a) and RT-qPCR of LAMTOR1 (b), LAMTOR2 (c), LAMTOR3 (d), LAMTOR4 (e) and LAMTOR5 (f) in fetal astrocytes transfected with miRNA-20a-5p mimic (miR20a) for 24h (n=3 biological triplets and 2 technical duplicates). Data is normalized to lipofectamine (control).
*p-value<0.05, **p-value<0.01, Mann-Whitney U test.
To the best of our knowledge the mechanism that activates the MAPK/ERK pathway in SEGA and other TSC lesions has not been determined. Previous studies have demonstrated that the Ragulator complex (LAMTOR1-LAMTOR5) is involved in lysosomal positioning, autophagy and the activation of both MAPK/ERK and mTORC1 pathways in the presence of nutrients and growth factors 29-31,87. It has been shown that the Ragulator complex is necessary for the localization and stabilization of RAG GTPases (RagA-RagD) and mTORC1 to the late endosomes/lysosomes membrane, which is required for amino acid-dependent activation of mTORC1 29,88. Furthermore, the Ragulator complex can also activate the MAPK/ERK pathway by recruiting MEK1 to the late endosomes/lysosomes 31,89. Although the involvement of the Ragulator complex in the mTORC1 and MAPK/ERK signaling
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